Observations regarding the rate of sedimentation of the erythrocytes are sufficiently ancient to lend dignity and interest to the problem offered by the variation of this rate in rheumatic infection in children. Galen 1 recorded that in certain conditions, particularly in severe infections, blood rapidly settled out, leaving a clear yellow serum. Several other clinicians made similar comments during the period when "blood letting" was popular. These observations were not crystallized into a test of value until 1897, when Bienacki2 proposed a method of measuring the speed with which red cells were separated from the plasma.There have been numerous modifications of his method, and the names of Fahraeus, Westergren and Linzenmeier are familiar in the literature on the subject. The basis of all the tests suggested is the time required for the erythrocytes to settle out of their suspension in the plasma. Fahraeus explained the change in the rate of sedimentation as due to variation in a property of the plasma, i. e., to a qualitative change in serum globulin, principally fibrinogen. On the other hand, Ernstene 3 showed that the important factor influencing the rate was the quanti¬ tative variation in the fibrinogen. The amount of fibrinogen and the rate of sedimentation of the erythrocytes are increased in many dis¬ eases, such as suppurative processes, contagious diseases, rheumatic infection, pneumonia, tuberculosis, syphilis, anemia 4 and leukemia. The fibrinogen is decreased in degenerative lesions of the liver. Venous stasis is another important cause of decrease in the rate of settling out of the red cells.

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